feat: major project restructure - move Django to backend dir and fix critical imports

- Restructure project: moved Django backend to backend/ directory
- Add frontend/ directory for future Next.js application
- Add shared/ directory for common resources
- Fix critical Django import errors:
  - Add missing sys.path modification for apps directory
  - Fix undefined CATEGORY_CHOICES imports in rides module
  - Fix media migration undefined references
  - Remove unused imports and f-strings without placeholders
- Install missing django-environ dependency
- Django server now runs without ModuleNotFoundError
- Update .gitignore and README for new structure
- Add pnpm workspace configuration for monorepo setup

static/js/park-map.js

@@ -1,29 +0,0 @@
-// Only declare parkMap if it doesn't exist
-window.parkMap = window.parkMap || null;
-
-function initParkMap(latitude, longitude, name) {
-    const mapContainer = document.getElementById('park-map');
-    
-    // Only initialize if container exists and map hasn't been initialized
-    if (mapContainer && !window.parkMap) {
-        const width = mapContainer.offsetWidth;
-        mapContainer.style.height = width + 'px';
-
-        window.parkMap = L.map('park-map').setView([latitude, longitude], 13);
-        
-        L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
-            attribution: '© OpenStreetMap contributors'
-        }).addTo(window.parkMap);
-
-        L.marker([latitude, longitude])
-         .addTo(window.parkMap)
-         .bindPopup(name);
-
-        // Update map size when window is resized
-        window.addEventListener('resize', function() {
-            const width = mapContainer.offsetWidth;
-            mapContainer.style.height = width + 'px';
-            window.parkMap.invalidateSize();
-        });
-    }
-}